In recent years, there has been a rapid advance in the development and market introduction of vehicles other than automobiles that travel by means of internal combustion engines, such as electric automobiles and hybrid automobiles, or ones that travel by means of motive power from electric motors, like fuel-cell automobiles. In many air conditioners for such automobiles whose motive power is provided by electric motors, with regard to compressors that compress and feed refrigerant, electric compressors whose motive power is derived from the electric motors serving as a driving source are also employed.
In addition, air conditioners for automobiles that travel by means of motive power from internal combustion engines also include those that employ electric compressors instead of compressors driven, via electromagnetic clutches, by the internal combustion engines used for traveling in order to alleviate the deterioration in drivability associated with contact breakages in the electromagnetic clutches.
As such electric compressors, sealed electric compressors in which electric motors and compressors are built into and coaxially integrated in a single housing have been employed, as disclosed in FIG. 1 of Patent Literature 1. As with many other electric compressors, the electric compressor disclosed in Patent Literature 1 is formed by joining a compressor-side housing, which accommodates a compressor, and an electric-motor-side housing, which accommodates an electric motor, and a partition member is disposed therebetween so as to separate them.
Then, a rear end and the vicinity of a front end of a main shaft of the electric motor are supported with a large-diameter main bearing that is press-fitted to the partition member and a small-diameter sub bearing provided at a back portion of the electric-motor-side housing. A rotor that forms the electric motor is provided at an intermediate portion of this main shaft so as to rotate integrally together therewith. The rotor is generally shrink-fitted to the main shaft. In addition, the front end of the main shaft protrudes into the compressor-side housing and is connected thereto to drive a rotational compression member that forms the compressor.
With the electric compressor of Patent Literature 1, the main-bearing outer diameter is made smaller than the rotor outer diameter. By making the main-bearing diameter smaller than that of the rotor in this way, a structure around a connecting portion between the main shaft and the rotational compression member of the compressor can be made more compact, the weight thereof can be reduced, and the assembly thereof can be simplified.
As for the main bearing, an outer race (outer wheel member) thereof is press-fitted to the bearing bore portion formed in the partition member from the electric-motor side, and the outer race is brought into contact with a positioning flange formed at an inner circumference of the bearing bore portion at the end thereof on the compressor side, thus setting the position thereof. In addition, a bearing journal portion formed in the main shaft is press-fitted to an inner race (inner wheel member) of the main bearing from the compressor side, and the inner race is brought into contact with a positioning flange formed at an outer circumference of the bearing journal portion at the end thereof on the compressor side, thus setting the position thereof. Here, expressions “press-fitted from the electric-motor side” and “press-fitted from the compressor side” indicate from which side of the partition member or the main bearing the press-fitting is performed; it does not indicate that the press-fitting is performed inside the housing of the electric compressor, and the individual press-fitting procedures are actually performed in a state in which the partition member, the main bearing, and the main shaft are outside the housing of the electric compressor.
In this electric compressor of Patent Literature 1, the assembly order of the main shaft, the rotor, the main bearing, and the partition member is presumed to be as follows. Specifically, the assembly order is such that, first, the outer race of the main bearing is press-fitted to the bearing bore portion of the partition member from the electric-motor side; next, the bearing journal portion of the main shaft is press-fitted to the inner race of the main bearing from the compressor side; next, the rotor is inserted into a rotor press-fitting portion formed at the intermediate portion of the main shaft from the electric-motor side and is shrink-fitted thereto; and, finally, the rotor is cooled, which establishes the shrink-fitting.